1. Field of the Invention
One or more embodiments relate to a fuel cell system using methanol as a direct fuel (hereinafter, referred to as a direct methanol fuel cell (DMFC)).
2. Description of the Related Art
In general, fuel cells are devices that directly convert chemical energy included in a fuel into electric energy by chemical reactions and are a type of energy generating devices that continuously generating electricity if fuels are supplied thereto. A direct methanol fuel cell (DMFC), which is a type of fuel cell, uses methanol as the fuel and has methanol supplied to an anode of the DMFC so as to react with oxygen supplied to a cathode of the DMFC to generate electricity. At the anode, the reaction represented by Formula 1 takes place, wherein electrons are generated and moved to the cathode along an electrical circuit, thereby causing the reaction represented by Formula 2. If a device requiring electricity is placed as an electrical load in the electrical circuit, tasks requiring electricity can be performed.CH3OH+H2OCO2+6H++6e−  [Formula 1]3/2O2+6H++6e−3H2O  [Formula 2]
Using only one assembly including one anode and one cathode, in which the reactions represented by Formulae 1 and 2 take place, may not generate sufficient electricity, and thus a stacked-form assembly is used.
A DMFC system denotes an entire device for supplying methanol and oxygen to the stack, generating electricity using the methanol and oxygen supplied, and re-circulating and re-using water, which is a product of the reaction of Formula 2, un-reacted methanol, and by-product water. In the DMFC system, if loss of highly-volatile methanol due to evaporation is minimized and the range of fluctuations in the concentration of methanol in the stack is reduced, a stable DMFC system can be realized.